I am getting really tired of getting emails and PowerPoint presentations in which half of the words are bold and underlined. There is also excessive use of exclamation points, all caps, and overly strong wording.

I would like to send them a link to someplace authoritative that states that their writing style is tacky. Is there anything like that out there? I would even settle for a blog post somewhere so long as it argues the point well.

The most-authoritative page I've seen on this topic is part of a style guide at Western Michigan University. It first points out that most of the recommendations in the guide “are consistent with AP style, which is the standard for the styleguides of most universities and for writing for the Web”, and later lists the following as errors to be avoided, because they create print and electronic publications that are unattractive and difficult to read: